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4 BBL Carb on a 225 V6 Articles

mtntinker's Edlebrock 4BBL Advice

4BBL V6 General Information

There are after market intake manifolds available for the 225 V-6. Two are the Weiand four barrel intake part #7541 and the Offenhauser 360. Even-fire 231 intakes have been said to work if you use a '78 or older intake gasket. Be advised that a four-barrel upgrade may cost some low-end horsepower. Engine parts are said to be available from Kenne-Bell and Kanter Auto Parts, among others. Information on both companies is available via the internet.

From the Willys Tech List:

Subject: Holley 390 cfm on a Buick 225?

Has anyone out there put a Holley 0-8007 carb (390 CFM 4bbl) on a 225?

How does it compare to the Rochester 2GC? I have a Rochester on now that needs a rebuild. (accelerator pump hosed and float saturated) Plus I would like an auto choke and the better gas mileage of a 4bbl.

I have the original intake manifold on now; do I need a new one for the Holley? The one they offer is EGR compatible, and I don't want to worry about EGR. This is going into my '55 CJ-5 after the paint job. I just run dual pipes with mufflers only. The only emission control I want is PVC.

I am not doing anything else to the engine- it has good compression and doesn't burn any oil.

Also, vacuum or mechanical secondary? The rest of the drive train is original, and no overdrive.

The information that I have isn't specific to the 225 and is a bit dated but it might help a little anyway:

Re: An automatic choke

A 4bbl gets better mileage than a two? That surprises me - live and learn. I agree an auto choke would be nice.

Re: Do I need a new manifold that is EGR compatible

The 'EGR compatible' manifold should have a port for an egr valve if you have one. They used to come with a block off plate if you didn't. If you don't replace the manifold you will need a 4-2 barrel carb spacer. The efficiency of the flow is hurt a little bit but the spacer should be a lot cheaper (and less labor intensive) than a manifold.

Re: Vacuum or mechanical secondary? The rest of the drive train is original, and no overdrive.

I would go with vacuum secondaries - that way they will kick in only when you really need them (and hopefully cut down on the gas bill). (If you're racing you'd want the mechanical.)

Re: Lower gas bill with a 4 bbl?

Well if you think about it the primaries on a 4 bbl are smaller than on a 2bbl right? We have a Ford truck with the 460 in it and the 4bbl helps it pass smog better because of that (smaller primaries on the 4 bbl.). I would guess that if you didn't have a lead foot than you could do fairly well with a 4bbl. If you tend to get a lead foot than David (see above) is right the 4bbl will be more costly. I would also choose the vacuum if your offroading it helps when you need it the one on the for mentioned above is a vacuum and it works great when you put your foot into it going up a hill so that would be my suggestion.

I stood in your shoes back about 16 years ago with a worn out Rochester. I was talked into an AFB and an offy "C" manifold. I pretty much lost the bottom end having to run a gear lower to keep the revs up. I don't know if it was the carb or the manifold. Last summer I bought a Kenne Bell manifold and a the 0-8007. The manifold wouldn't work as it was too tall and I will not cut a hole in my hood. I put the Holly on and went to Silverton, CO for the summer. I had to re-jet it a couple of times because of the altitude. It ran very well, but I had a stumble just over idle. Carb or intake? I know not. It did work better than the AFB. I was told that a Q-Jet is the best for what I wanted. For this summer I'm going to use the Holley and try the Holly intake I got from the guy in Oregon that someone on the list found. I'll give the 4 barrel one more try. If it doesn't work it's back to the two-barrel and all that other stuff was not worth it. I did meet a fellow from Texas with a CJ-5 and V6 who swore by the two barrel. Ya know as I recall, I never once had a problem with the Rochester and had the 2a over 80mph even before the overdrive. (Now how bright was that?) I would have saved myself a lot of work by sticking with the 2 barrel, but it wouldn't have been as much fun. Don't forget to save your old intake, you never know when you will need it.

I have been following this thread for a while, and feel I have a bit to add. First, about the Rochester carbs. The two barrels fitted by GM to these engines were of the 2G series. For these engines, 2Gs come in two major varieties 2GC and 2GV. The 2GC has an integral automatic choke control mechanism (C means choke). The 2GV has a vacuum break, which pulls off a choke as set by a manifold mounted thermostat. This is the divorce mounted thermostat, typically a bi-metallic spring coil in a well located in the exhaust crossover (2GV means vacuum). 2G series RPD carbs w/ 1-11/16 throttle bores come in four basic flow ratings:

Question: So is there a factory 4 barrel intake for the 225?

No. The 231 however was available with a 4 bbl in the late 70s. Now the heads changed somewhere along there (79 I think), and I don't know if the early 231 heads were the same as 225 heads. The later heads were I believe totally different, and not compatible. 231 manifolds (75 & later) will have EGR valve provisions. IMHO, if faced with a late motor, I would look for one new enough to have fuel injection and quit messing with carbs altogether. It seems to me that Weiand makes a couple of aluminum intakes for the 225s. one is fairly mundane and the other is definitely a HP item and would not work well in a Jeep. Edelbrock makes a Performer for the 231, but I think it is for the later heads. Intake runner volume is the thing to consider here. While big ports flow well at high RPM, they hurt mixture velocity down low and kill response. Plenum volume should also be considered. Try Kenne-Bell, T/A Perf., or Poston for Buick specific goodies, they are the experts. As far as a 4 bbl killing low end torque or hurting MPG, I don't buy it. The carb will only admit as much air into the engine as the operators right foot tells it to. A small 4V carb has much smaller primary venturris and will see a stronger vacuum signal at low rpm or at cruise. Therefore the response should be better, and the metering more accurate. The Holley is a vacuum secondary carb, and the rear barrel opening is controlled by the amount of air entering the engine. Set up properly, they should be resistant to bogging, even if the operator floors it at low RPM. By comparison, if a 2 bbl is opened all the way at low RPM, it admits far more air than the front half of a 4 bbl, and relies totally on the accel-pump shot to mask any stumble. Not only will this use more fuel, but the momentary richness at low RPM does nasty things to piston rings. Tuned properly, the 4V carb will get no poorer fuel economy than the 2V.

It takes a certain amount of fuel to move a vehicle down the road no matter how it is delivered. The big reason MPG drops is the operator tends to use the added power capacity and simply puts more fuel into the engine. The right foot strikes again. As an aside, Holley carbs with low profile air cleaners (like in a flatfender CJ) don't work well, but for other reasons. Frankly, I have always felt that the RPD 2V carbs have been rather unresponsive for the amount of fuel they use. Remember 2 bbls were typically installed for economy reasons. Not fuel economy, but manufacturing economy, as 2 bbls cost far less to manufacture than Quadrajets. Hope this helps.

Tuned properly

That's the key phrase, "tuned properly". I doubt most of us can tune a carb/manifold better than the factory. There is no factory 4 barrel manifold for a 225. Most after market manifolds, even the mild ones, were designed for a higher rpm range than factory, which means the low end suffers some. If you want more power go for it. If you just want it to run well stick with the factory setup. My comment was "if the rest of your engine is stock, stick with the factory carb". My jeep probably spends more time running around 1000 rpm than it does at even 3000. If I wanted more power I wouldn't try to squeeze it out of a 225, I'd put in a V8.